This invention is in the field of safety devices for distributing the carrier liquid of a liquid-state chromatography apparatus.
A liquid-state chromatography apparatus successively comprises, in the direction of flow:
(1) A RESERVOIR FOR CARRIER LIQUID;
(2) A CARRIER LIQUID PUMPING SYSTEM, WHICH SUPPLIES THE CARRIER LIQUID TO THE SEPARATION COLUMN;
(3) A SYSTEM COLUMN WITHIN WHICH SEPARATION TAKES PLACE, THAT IS, WHERE THE SAMPLE IS SEPARATED INTO ITS VARIOUS COMPONENTS;
(4) A DETECTOR, OF A TYPE DEPENDING UPON THE MOLECULES TO BE DETECTED.
The separation column should be traversed by the carrier liquid at a low but constant rate of flow. In view of the substrate and length of the column, the head loss must be compensated by application of pressure on the carrier liquid upstream of the separation column. The use of pumps is avoided in the carrier liquid feed system of the usual chromatography apparatuses, since they are often fragile and expensive, and such pumps are the source of vibrations which lead to uneven flow of the carrier liquid and to background noise at the detector baseline. Thus, the use of pumps may be avoided by keeping the reservoir containing the carrier liquid under the pressure of a carrier gas of low solubility in the carrier liquid, the gas being contained in a compressed gas cylinder and furnished through a pressure regulator. It is necessary in this case to prevent the gas from mixing with the carrier liquid, which involves the risk of creating an emulsion at the exit from the column. The carrier liquid reservoir most often consists of a tube of small diameter wound helically to reduce its bulk. This reservoir arrangement reduces the contact area between the carrier liquid and the carrier gas, and the substantial length of the tube prevents bubbles of carrier gas from being driven to the base of the reservoir, from which base the carrier liquid is directed toward the separation column.
The use of a carrier gas requires certain precautions; its implementation is sensitive, particularly when the carrier liquid reservoir is being refilled. In fact, improper handling of the carrier liquid inlet valve, the overflow valve and the carrier gas inlet valve may result in premature emptying of the reservoir and forceful ejection of the carrier liquid.